OP0115 mtDNA D-LOOP VARIANT m.16519C INCREASES THE RISK OF RAPID PROGRESSION OF KNEE OSTEOARTHRITIS. A META-ANALYSIS AND FUNCTIONAL STUDY
Authors: A. Durán-Sotuela, M. Fernandez-Moreno, T. Hermida Gómez, P. Ramos-Louro, S. Relaño-Fernandez, V. Suárez-Ulloa, V. Balboa-Barreiro, N. Oreiro, C. Vaamonde-García, J. Vázquez-García, F. J. Blanco, I. Rego-Perez
Journal: Annals of the Rheumatic Diseases (2022)

Background The development of a tool capable of identifying patients suffering the rapid progressive knee Osteoarthritis (RPOA) was established as a goal to implement prevention strategies and to include them in clinical trials. Previous studies showed that mitochondrial DNA (mtDNA) variation plays a role on the incidence and progression of OA, but their influence on the development of RPOA is unknown. Objectives To find new mtDNA variants related to RPOA in order to develop a predictive model based on genetic and clinical variables. To find out the functional significance of these variants using transmitochondrial cybrids. Methods We used data from three independent prospective cohorts of patients: the Osteoarthritis Initiative (OAI) (N=1102) and the pooling of two European cohorts as replication cohort (N=706): the Cohort Hip and Cohort Knee (CHECK) and the Prospective Cohort of Osteoarthritis from A Coruña (PROCOAC). We classified the patients based on the following criteria: Rapid progressors (N Discovery=268, N Replication=107), subjects with baseline KL grade 0-1 and increase up to KL≥3 during 48-month follow-up; or baseline KL grade 2 and increase up to KL grade 4 during the follow-up. Non-rapid progressors (N Discovery=827, N Replication=592), subjects with the same baseline characteristics as rapid progressors, but with a slower or no evolution over time. mtDNA variants were screened in the OAI by in-depth sequencing. Resulting variant was analyzed in the replication cohort by mini-sequencing techniques. Appropriate statistical approaches adjusting for confounding variables followed by a meta-analysis were applied. We developed a functional study using two types of transmitochondrial cybrids carrying the most common haplogroup H: one harboring the mtDNA variant m.16519C and the other the wild type m.16519T. Cybrids were used to assess mitochondrial biosynthesis and mitochondrial fission/fusion by gene expression analyses, as well as cell viability to oxidative stress and mitochondrial reactive oxygen species (ROS) production. Results The in-depth sequencing of mtDNA showed the D-loop variant mt16519C significantly overrepresented in rapid-progressors (OR=1,558;95%CI=1,148-2,113;nominal p-value=0,004; Benjamini-Hochberg corrected p-value=0,044). The analysis of this variant in the replication cohort showed a similar significant trend (OR=1,647;95%CI=1,013-2,678; p=0,043). The logistic regression model revealed that, regardless of the different clinical variables, the variant m.16519C was significantly associated with RPOA in the OAI cohort (OR=1,559;95%CI=1,125-2,161; p=0,008) (Table 1). The development of this model in the replication cohort showed a similar trend that borderlined the statistical significance (OR=1,506;95%CI=0,848-2,675;p=0,162) (Table 1). The subsequent meta-analysis for both ORs showed the variant m.16519C significantly associated with RPOA (OR=1,58;95% CI=1,22-2,05;p=0,0027) (Figure 1). Table 1. Binary regression model including clinical variables and m.16519C in both cohorts. BMI: Body Mass Index; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; OR: Odds Ratio; CI: confidence interval; *: statistical significance declared at P &lt; 0.05 Figure 1. Forest plot of the meta-analysis of the ORs of the two predictive models Cybrids harboring the mtDNA variant m.16519C showed lower levels of PGC-1α (p=0,0024) and FIS1 (p=0,0519) than cybrids with the wild type. In addition, cybrids harboring the variant m.16519C showed lower average cell survival under oxidative stress conditions (23,42±8,88 vs 115,7±64,1;p=0,0043), as well as higher mitochondrial ROS production (4,21±1,29 vs 2,21±1,34;p=0,014). Conclusion D-loop variant m.16519C increases the risk of developing a rapid progression of knee OA. Among the effects caused by this variant both mitochondrial biogenesis and fission/fusion processes, as well as cell survival under oxidative stress conditions and mitochondrial ROS production seem to be affected Disclosure of Interests None declared